Vervoorn Maria v Mine Subsidence Board - [2007] NSWLEC 538

Land and Environment Court

of New South Wales

CITATION: Vervoorn Maria v Mine Subsidence Board [2007] NSWLEC 538

PARTIES:
APPLICANT
Maria Vervoorn
RESPONDENT
Mine Subsidence Board

FILE NUMBER(S): 30558 of 2006

CORAM: Talbot J

KEY ISSUES: Mine subsidence :- Proof of cause of damage - extent of attributable damage - appoinment.

LEGISLATION CITED: Mine Subsidence Compensation Act 1961 s 12, s 12A, s12B

DATES OF HEARING: 25/06/07, 26/06/07, 28/06/07, 29/06/07, 19/07/07, 20/07/07, 25/07/07, 30/07/07, 2/08/07, 6/08/07

DATE OF JUDGMENT:
29 August 2007

LEGAL REPRESENTATIVES:
APPLICANT
Mr D G T Nock SC
SOLICITORS
Barry F Cosier & Associates
RESPONDENT
Mr P McEwen SC
SOLICITORS
Trisley Kilmurray Lawyers

JUDGMENT:

THE LAND AND
ENVIRONMENT COURT
OF NEW SOUTH WALES

Talbot J

29 August 2007

30558 of 2006 Vervoorn, Maria v The Mine Subsidence Board
JUDGMENT

1 Talbot J: The applicant Mrs Vervoorn is the owner of a property in the town of Lithgow, known as 19 Birdwood Street. The house is in a dilapidated state and has become inhabitable as a consequence of severe damage throughout the structure of the building. Mrs Vervoorn has lodged a number of claims with the respondent Board over the years alleging that the damage or at least a major part of it is caused by mine subsidence. The latest claim lodged with the Board in December 2005 is the subject of an appeal to this Court. The claim for damages contains particulars of the nature of damage alleged by Mrs Vervoorn in her own words as follows:-

Significant cracking to the walls and floors of main portion of the double brick home and the bed-sitting room adjoining, both internally and externally with substantial movement allowing a free flowing of flies, spiders and warm air (cold air in winter).

Severe cracking and movement of the front verandah and patio area including the floor tiles (the original concreted steps collapsed and the replaced wooden stairs to the front door have also moved away from the home.)

Severe cracking to the concrete paths surrounding the home.

The AGL representatives have instructed the Applicant not to use the Natural Gas service owing to the severe movement of the ground where the gas metre is located and the lines past into the home. This has existed for the past two winters.

The Applicant believes that the home is well beyond economic repair.

2 Mrs Vervoorn says in the Claim Application form that the damage was first noticed “in about 1998.”

3 However earlier claims were made in early 1991 and March 1998. All claims have been rejected by the Board.

4 At the time Mrs Vervoorn bought the house it had a wooden floor in the front of the house. At the rear on the southern side there was a concrete slab. The slab had been installed after the house was built.

5 In 1991 Mrs Vervoorn complained about some cracking. However her main complaints commenced in 1998 when the house started to show major cracks.

6 The house is built partially over a mine roadway and partially over what is referred to as a T-junction at the barrier pillar. The barrier pillar adjacent to the mine roadway is the finish of the working. Originally there were railway lines branching off and a set of points at this location.

7 There is between 9.2 and 10.3 metres of overburden above the workings. There is a rock strata of between 7.9 up to 8.8 metres.

8 The applicant’s case arises under s 12 of the Mine Subsidence Compensation Act 1961. The appeal is made under s 12B. Section 12 relevantly provides: -

12 Claims for damage arising out of subsidence

(1) Claims may be made under this Act for payment from the Fund of:

(a) compensation for any damage to improvements that arises from subsidence, except where the subsidence is due to operations carried on by the owner of the improvements,

(b) an amount to meet the proper and necessary expense incurred or to be incurred as a result of such damage in:

(i) building retaining walls or bolting together or underpinning or otherwise supporting, raising or repairing buildings and walls,

(ii) altering the approaches to or the levels of lands or buildings,

(iii) raising, lowering, diverting or making good roads, tramways, railways, pipelines, bridges, fences, sewers, drains or other improvements,

(c) an amount equivalent to the rent which would have been payable for such period as may be prescribed in respect of any buildings or works which by reason of such damage are untenantable, under repair or in course of construction, or where such buildings or works or any part thereof are or is occupied by the owner thereof such sum in lieu of rent as the Board deems just,

(d) compensation for any damage to household or other effects that arises from subsidence, except where the subsidence is due to operations carried on by the owner of the household or other effects.

No claim shall be entertained or payment made under this Act in respect of any improvement which was the subject of a conditional right to insure granted under section 16 of the Mine Subsidence Act 1928 unless the conditions of such conditional right have been, and are at the date of making such claim, complied with, or, where such conditions have not been or are not being so complied with, unless the Board is satisfied that any departure from or contravention of such conditions is such that it need not be rectified.

Where damage, caused by subsidence, to an improvement is greater, by reason of the negligent or improper manner in which the improvement was constructed or maintained, than it would have been had the improvement not been so constructed or maintained, the Board may reduce the amount of compensation in respect of the damage by such amount as it considers is attributable to the fact that the improvement was so constructed or maintained.

(1A) Notwithstanding anything contained in subsection (1) or (2), or section 12A, or any approval given under section 15, where:

(a) improvements or household or other effects used in connection with the carrying on of an extractive industry or operation were damaged by subsidence before, or are so damaged after, the commencement of the Mine Subsidence Compensation (Amendment) Act 1969, or

(b) expense referred to in section 12A (1) (b) was incurred before that commencement, or is incurred or proposed, in relation to any such improvements or household or other effects,

the Board may refuse to entertain a claim, or make a payment, in respect of that damage or expense where it is satisfied that the cause of the subsidence that caused the damage or necessitated the expense was the carrying on of that industry or operation.

(2)

(a) The owner of any improvement or any household or other effects which have been damaged by subsidence may notify the Secretary of the Board in a form approved by the Board and within the prescribed time of the details of such damage; the location of the improvement damaged; the description of the household or other effects damaged; the amount claimed from the Fund and such other particulars as may be prescribed.

Such notification shall be treated as a claim for payment from the Fund under subsection (1).

(b) Any such notification received shall be recorded and investigated by the Board, an officer of the Board or some other officer in the Public Service acting for the Board and on receipt of a report of such investigation the matter shall be placed before a meeting of the Board for a decision as to the payment, if any, to be allowed in respect of the damage to which such notification relates.

(3), (4) (Repealed)

(5) Payments may be made under and in accordance with the provisions of this Act notwithstanding any covenant, condition, stipulation or restriction affecting, limiting or restricting the recovery of damages or compensation for damage arising from subsidence to improvements or household or other effects in respect of which a claim for such payment has been made.

9 Section 12B provides that a person claiming compensation under s 12 or s 12A may appeal to the Land and Environment Court against the decision of the Board:

(a) as to whether damage has arisen from subsidence or could reasonably have been anticipated, or

(b) as to the amount of the payment from the Fund.

10 Section 13 allows for the Board to purchase the land or the improvements in lieu of making payments in respect of claims under s 12 or 12A(1)(a).

11 I agree with Mr Nock S.C who appears for the applicant, that there is no issue about the following:-

(a) the original house was built more than 80 years ago.

(b) It consists of cavity wall brick construction and has probably been extended at least twice during the course of its lifetime.

(c) The house is built on a sloping block which slopes towards the north fronting Birdwood Street.

(d) The front of the block is sloping north with at least one high retaining wall and two lower retaining walls. There is a set of concrete stairs extending from the street level in 2 flights up to the front of the house where a path runs east west and leads to a verandah.

(e) The property was purchased by Mrs Vervoorn in 1989.

(f) Mrs Vervoorn made her first complaint to the Board on 29 January 1991 in respect of mine subsidence which was rejected by the Board.

(g) In 1997/98 Mrs Vervoorn made a further complaint concerning possible subsidence.

(h) In 1998 the Board began monitoring the area of the house.

(i) In 2004 Mrs Vervoorn made the present complaint.

12 The respondent’s experts say that the following possible causes are: -

· Reactive soil - reaction of the soil to water.

· Soil creep – the movement of soil down a hill.

· Poor foundation design.

· Landslip.

· Groundwater flow.

13 The Board’s case is that the possibility or even probability of subsidence is not supported factually. It is submitted, there are three mechanisms responsible for any damage coupled with inadequate footings and foundations. They are soil creep, groundwater movement and reactive soils.

14 Mr Nock S.C, contended at the opening that the evidence would show that periodic survey measurements taken at the back of the house on the southern side are going down and those at the front have gone up at times and down at other times.

15 It is claimed by the applicant that the way in which the house is moving is that the slab itself is moving downwards and twisting to the east. The result is that it is going to the south and to the east. The applicant’s experts say that the survey readings are not consistent with soil creep, as, if there was soil creep the movement would be to the north. Moreover, if the cause of the damage was soil creep then it could be expected the cracking in the building would commence at the bottom and spread upwards. They say the cracking is more at the top and comes in at the bottom. That is a process called hogging caused by the bottom of the building remaining relatively in the same position while going down. The cracks therefore open further at the top. As movement is only vertical it is consistent with subsidence. Soil creep requires two components. First a horizontal component and secondly a vertical component.

16 In this case, it is alleged one side is dropping into the space created by the subsidence.

17 The applicant notes that as the soil type is of a moderate to low level of reactivity it is not of a type that is expected to give a great deal of reaction. Soil reacts to water and it expands. If water is taken out of it, it contracts. Some soils remain stable. The applicant’s experts say that the amount of damage to this house and the way in which it has occurred is totally inconsistent with anything to do with reactive soil.

18 The applicant relies on the evidence of Dr Leon John Ernest Thomas to say that the floor of the workings show clear evidence of water coming through the strata above the workings and heading down hill. In some of the bore holes drilled for the purpose of investigation, water was noted to be seeping down the hole into the area. This he says was visible in a CCTV film taken by a camera lowered through a bore hole.

19 Mr Nock alleges that, there has been movement particularly at the T-junction. It has been movement sufficient to allow the surface to start to subside, although not sufficient to collapse the workings. Dr Thomas argues the subsidence has been caused by the weight of water slowly penetrating and then being able to disappear, as it were, into the void. The process of the water penetrating takes with it particles of material. Over a period of time it gradually takes away some finer particles. The applicant’s witnesses cannot say that some of the water may not have come from a reservoir above the Vervoorn’s property. However, it is claimed that the damage would not have occurred if the mine void had not been there.

20 In summary, it is contended on behalf of the applicant that the hinging effect that has occurred in this case is not consistent with slip or some other surface defect. Soil creep is eliminated. The reactivity nature of the soil is discounted. There is a prospect that the water has caused the roof to sag. The intervening stratum between the surface and the roof has consolidated as a consequence of the washing through. The washing through would not have occurred if there was no void.

21 There is considerable controversy in respect of the way in which the survey data should be understood and interpreted. Even counsel had difficulty in reaching a consistent and certainly common position in relation thereto.

22 Mr McEwen SC, who represents the respondent Board, notes that an original claim based upon an alleged sagging beam has given way to the theory in respect of water penetration namely, that percolating water would carry fines such as to allow the soil above the percolating area to lose its stability and subside. His answer to the theory put forward by Dr Thomas is that the levels show that the rear of the house has been rising for a period of time contrary to the normal expectation for subsidence and that movements of the house extend outside the T-junction and therefore do not correspond with the location of the T-junction.

23 The levels show the ground is subject to cyclical periods of rising and falling. According to Mr McEwen this is inconsistent with subsidence behaviour. That he says is the ultimate question.

The Expert Witnesses

· Dr Thomas is a mining engineer instructed by the applicant.

· Gregory Phillip Kotze is an engineering geologist specialising in slope stability. He is retained by the applicant.

· Dr Lawrence Peter De Ambrosis, is a geotechnical engineer who is also engaged to advise the applicant.

· Professor James Morris Galvin, the Emeritus Professor in Mining Engineering at the University of NSW with qualifications in mathematics, mining engineering and rock mechanics has given evidence on behalf of the respondent.

· Leigh Davin Appleyard, is a civil and structural consulting engineer advising the Board.

· Gregory Charles Hawkins gave evidence for the Board as an expert engineer specialising in geology.

24 After preparing various reports, joint conferencing and considering the survey evidence and carrying out personal inspections of the property the six experts were required to give their evidence concurrently. A joint statement asserted as having been produced in accordance with the Expert Witness Practice Direction, during the first day of the hearing, was prepared in such a way that it neither complies with the Court’s expectation nor provided any significant assistance. Their oral evidence in chief during the concurrent session is usefully summarised as follows for each individual.

Dr Thomas

25 Dr Thomas explained that in his opinion the mode of failure demonstrated by the data in respect of Mrs Vervoorn’s house, is a straightforward textbook example of shallow roadway practical rock mechanics. The rock in this case is buried deep enough not to have any elastic compression or any substantial deformation. It is essentially dead weight deformation.

26 Dr Thomas explained that all rocks have a sheer strength that differs. Over a period of time a network of cracks appears through the surface. As water comes through it tends to wash out the small grains thereby lubricating the horizontal bedding plains enabling the individual rocks to move past each other. Sometimes clay material is washed down and provides further lubrication. An unstable structure is created whereby small pieces of rock are chaffed. There is never really an enormous lowering into a roadway or void. The movement is small. The pattern of fractures and settlement goes to the surface. All of the joints are worn away to a small extent. Eventually at the surface there are small depressions in the order of 50mm -100mm.

27 In relation to the Vervoorn house, there is a sequence beginning with coal which is a tough woody material immediately over the roadway with some tensile strength. It will sag slightly over the roadway between 10mm and 20 mm in the middle with some sheering at the edges of the pillars. It will pan across an opening if there is sandstone above to help support it. Above the sandstone there is some siltstone. Above that there is a pebbly coarse sandstone followed by a mix of carbonaceous siltstone. Above that again there is some weathered shale. Accordingly, there are two strong beds and some weaker beds.

28 Dr Thomas says: -

The softer materials can wear away much more easily and the clay weathered shales, silt stones, at the top of the sequence, can break up and wash away, and go down through these fractures in the rock, and if you have really heavy rainfall you can steadily lose maybe sort of a few millimetres of material each time, and the weathered shales becomes a bit honeycombed porous, you have cracks in them, and they will start to settle under their own weight.

29 He went on further to say: -

It’s a progressive settlement from the bottom roadway up, but probably from experience most of it is happening in, say, the top third of the sequence because that’s where the action is taking place. You find this sort of exposure as a fairly regular thing because rocks behave the same way. It was my speciality to go and look at rock forms.

30 He says that a fracture pattern will be found above any intersection, T-intersection or square intersection.

31 To his mind the bore hole cores and bore hole logs show the sort of disturbance in them that he would associate with the type of deflection and fractures he has identified. He says that the upper part of the borehole logs show water loss and cavities and that the pictures show an increasing flow of water down the borehole. The water that is coming down through the borehole is actually coming from the intervening strata and it is running down into the mine underneath.

32 Dr Thomas recognised that it could have been more helpful for the purpose of ascertaining the actual movement in the ground if the survey points had been located on the ground.

Mr Kotze

33 Mr Kotze said he can find no evidence of large scale or even significant landslides or landslip affecting the residence. He could see no evidence of slope creep around the rear and central portions of the subject allotment. He considers the actual residence to be a substantial structure that had been there for about 80 years. Accordingly, he concluded that it was not soil creep that was adversely impacting the core of the house or that was creating the extensive damage to the residence.

34 Testing of the soil showed that it could be classified as class S to class M. Class S is the lowest category of reactivity; “S” standing for slightly. The test results show the soils were slightly to moderately reactive to changes in moisture content. That can typically create minor cracking under some conditions but the extent of the damage to this residence is not minor. The house is uninhabitable. In his assessment, shrink/swell soil has not caused the damage to the residence. He observed a general pattern in the cracking in the house. The cracks were most often more widely open at the top. That indicated to him that there was a possibility of a relationship between the cracks, the damage and the mine workings in close proximity. He therefore elected to seek advice from his colleague Dr de Ambrosis.

Dr de Ambrosis

35 Dr de Ambrosis observed the crack pattern and concluded that it was indicative of movement in the house walls and floor. It only fitted ground settlement at the uphill end of the house. The ground settlement was too large to be due to soil reactivity given the low to moderate reactive nature of the site. He came to the opinion that the settlement could only be due to settlement of the overburdened strata into the mining void. He discounted soil creep or land slope instability as possible causes. The reason he says this is because of the crack pattern in the house. He regards this as the key indicator to the mechanism causing damage. The pattern is not consistent with damage that would be caused by soil creep or slope instability. Soil creep will produce cracking that starts in the foundation brickwork and propagates up to the top of the wall. The crack pattern caused by soil creep will exhibit uniform lateral horizontal openings over the entire height of the crack and horizontal components of the cracking. It generally follows the mortar in brickwork. With soil creep you tend to get opening at the bottom half. Moreover, if the causation was soil creep, the vectors of movement of the monitors placed on the house would show predominate downhill movement. Uphill movement is consistent with rotation at the top of the back of the house. Soil creep has only one component, namely downhill.

36 Dr de Ambrosis discounted footing settlement as a cause as there is no indication of that occurring.

37 He has prepared diagrams to show the apparent contrary behaviour of the cycling. Some uplift with settlement. He says it can be explained by mine subsidence. Moreover, the point to understand is that what is being monitored is the reaction of a rigid structure, the brick walls, to what is an irregular stepwise ground settlement. As the ground settles the wall follows that ground settlement down. There are monitoring points at either end of the wall. One end has settled more than the other end. It moves further down causing the other end to “kick up”. He says that explains the cycling. Because the hinge point is being moved over successive movements that is described as hinging. That is not creep movement. Dr de Ambrosis describes it as “bending of the ground surface in the uphill direction”. The ground does not hinge. The ground curves. Dr de Ambrosis summarised his position as follows: -

“Motion of the wall downwards as the ground settles will not necessarily be uniform and smooth. A somewhat jagged downward motion can be expected where if the motion is observed in small time steps. The jagged motion can be observed as comprising a series of steps or rises and falls”, however, and this is important and the key “the overall net movement is downwards in keeping with the overall settlement into the void. It’s clearly demonstrated by the wide cracks in the house and the monitors in the south-west corner of the house”.

Professor Galvin

38 Professor Galvin first became involved in the investigation of the damage as an advisor to the respondent Board by critiquing work of consultants for the Board. Professor Galvin explains that when dealing with ground movements one of the key and fundamental tools used are survey measurements. It is also important to understand what the underground workings look like, as a matter of fact. He regards the survey information as only relevant to the date it was taken. There is no information in relation to what occurred in between those dates.

39 He explained vector movement as simply the horizontal component of a movement. Survey stations were originally installed in 1995. He observes that in 1995/1996 the measurements show that in general the ground had a tendency to be moving up. The survey data presented demonstrates to Professor Galvin that the whole area surrounding the Vervoorn house is undergoing cyclic movement, periods of rising and falling.

40 There are a number of matters that the Professor took into account: -

1. Soil in the vicinity of Mrs Vervoorn’s house is moderately reactive.

3. There are only four measured points that show movement in excess of 20mm; one is 23mm; two are in the range of 30mm and two are in the range of 40-50mm. The two in the range of 30mm are marked on a slab at the front of a lean-to on the side of the house. It is not keyed in to the house. The other two points showing movement of 40-50mm are located on the extension of the rear of Mr Vervoorn’s house.

4. Obviously something happened before 1995 that caused Mrs Vervoorn to first bring this matter to the attention of the board. That was in 1991. He assumes something else happened to trigger the installation of survey stations in 1995.

5. Mine Subsidence movements are in a downward direction.

6. Uplift occurs around the edges of the workings, associated with very strong rigid stratum that overhangs the workings.

7. The old workings are in pristine condition.

41 The fact that the workings are in pristine condition and the survey information are points of fact that cause him to be of the firm opinion that the most likely causes of damage, wholly probable cause of damage, is reactive soil.

42 He also notes evidence that there are signs of soil creep and that there are groundwater changes to be considered. Therefore this is not just a case of reactive soil, but rather a number of these parameters acting together.

43 Although he relies on others for the expertise in relation to the other factors, it is his firm opinion that reactive soil is the most probable mechanism, although the others such as soil creep and groundwater contribute to the cause of the damage. In his opinion there is an extremely remote possibility that the damage is related to mine subsidence. According to his view the underground observations and the lateral distribution of settlement does not make sense, in the context of subsidence.

Mr Appleyard

44 Mr Appleyard says that he has developed specialisation in the area of assessing buildings and structures impacted by the effects of the underground coal mining and has acted on many occasions as an expert retain by the Mines Subsidence Board (MSB) as well as private individuals. It has been his consistent view throughout the investigation of the damage to the Vervoorn residence that the damage is not the result of mine subsidence. He concedes that it is possible for ground surfaces to temporarily increase in height ahead of modern mechanised long wall mining operations whereas the mining in the present case took place at least 80 years ago using the conventional board and pillar mining. He says there are three main manifestations of damage to surface structures which may result from undermining operations. These are:-

1. Whole scale lowering of the ground surface and the structures built thereon.

2. The transfer of ground strains into the footings of a structure.

3. Residual tilt which occurs when vertical translation is uneven.

45 Mr Appleyard said it is generally accepted that shallow footings such as those upon which Mrs Vervoorn’s residence is build are least likely to be affected by the transfer of ground strains. He has seen no evidence “whatever” which suggest that any of the observed damage to the subject property is as a result of ground strain transfer. However, he makes general observations about the type of construction used as being out of date as well as a quite “unorthodox construction” of the floor under an external verandah and the lounge room. Having regard to the minimal headroom available he explained that it would be necessary to carry out some invasive investigation works externally to determine the precise construction details of the footing system in this area. This has not been done. Nevertheless, he considers it “highly likely” that the foundation material under the footing system of an extension remains significantly wetter than other footings around the house.

46 It is his belief that the northern part of the residence has been damaged by a combination of soil reactivity and down slope soil movement while the front stairs have moved away from the residence due to inadequate footings bearing on materials susceptible to down slope soil movement. He also believes that an addition on the western side has also moved away from the residence due to inadequate footings and inadequate bonding into the building itself. It is his believe that the southwestern portion of the residence, including the abovementioned addition has settled due to a combination of poor construction practices and overloaded original footings founded on wet and compressible soils.

47 Notwithstanding his lack of mining engineering expertise he concludes from a viewing of the CCTV that there is no indication whatever of any form of distortion or settlement likely to give rise to mine subsidence. Moreover, he says the random pattern of fluctuations in surface levels around the dwelling is entirely consistent with ground movements due to any of a combination of other factors. In his view a random pattern of fluctuations is entirely inconsistent with mine subsidence induced surface deformations.

Mr Hawkins

48 Mr Hawkins commenced work in relation to investigation of the Vervoorn residence in June 2005. He inspected the site, reviewed the core samples and the assessment of the pillars. He also carried out shallow soil sampling for shrink-swell testing to assess reactivity. He undertook the CCTV inspection that is recorded on videotape. He noticed no fractures indicative of fracture zones or faults as a consequence of the drilling operation.

49 The magnitude of characteristic movement in the soil from shrink-swell behaviour was measured as 10mm, 15mm and 30mm. The 15mm was measured in the back garden whereas the other two measurements were taken in front of the house. The characteristics settlements were those expected under the range of climatic conditions.

50 The mine records show that the road workings were excavated well before the house was built. Mr Hawkins calculated the factors of safety of the pillars which ranged from 16 to 213. At that level he would definitely never expect pillar failure or pillar creep.

51 As mentioned above the video which he recorded did not indicate any fractures zones or faults. Where partings were present the aperture was less than 1mm thick. Iron deposition has been flowing over sections of the annular ring round the inside of the bores. According to Mr Hawkins this shows deposition of material, not erosion.

52 The video shows the mine layout as essentially similar to the record traces for the mine, although it is further up slope than previously anticipated by earlier efforts to match the record traced to the surface. There is no significance spalling from the walls of the pillars and there is very little material accumulated on the floor at the base of the pillars. The roof is clearly intact with very few areas indicating that there has been any fall of rock from the roof. It is relatively stable. He observed nothing that could cause movement. The absence of substantial dripping of water from the roof and the lack of brown stains on the roof leads him to conclude that the water observed flowing into the mine from the bore hole is not normally found in the system above the coal and under normal processes has not reach the coal mine.

53 If the movement detected in the survey monitoring of the residence was related to mine subsidence Mr Hawkins expects it would be at 90 degrees to the centre line of the roadway or diagonally toward the T-intersection. In that respect he makes the following observations in relation to the survey monitoring of the house:-

What’s actually happened in the monitoring that’s available is that the south-western - the movement basically of the south-western corner has been out to the south-west, the movement at the north-eastern corner has being out to the north-east and at other times in the survey, the south-western corner has moved to the east parallel to the wall. These directions of movement are obliquely out into the workings but not towards the centre line or in the case of the ones that are to the northeast essentially parallel to the direction of the mine workings. Now I also note that you had a similar direction of movement on the boiler room which is well removed in the mine workings and clearly not related to mine subsidence

54 He agrees that there may not be one single factor causing movement of the house and recognises the prospect of construction problems, soil creep, soil reactivity, as well as discharge of water from upslope near reservoirs on the top of the hill above the Vervoorn residence. However, his comments in relation to possible causes are not definitive because his brief from the Board was only to determine whether or not the cause was mine subsidence.

Cross-examination of the applicant’s expert witnesses

55 Cross-examination by Mr McEwen concentrated on contrasting statements in reports prepared individually before the joint conferencing process began. Whereas previously Dr de Ambrosis, to some degree, had expressed opinions beyond his specialised expertise he now confines his evidence to the concise area of his expertise which does not extend into the mechanics of mine subsidence. He defers to Dr Thomas in that respect. Each of the applicant’s witnesses maintained their respective position essentially as outlined in the primary final statements made in the course of the concurrent sessions.

Further oral evidence of the respondent’s expert witnesses

56 Cross-examination of the respondent’s expert witnesses needs to be dealt with in some detail, as Mr Nock launched a major attack on their respective ability to adopt the degree of independence from the Board as demanded by the Court in its Expert Witness Practice Direction.

57 In answers to questions from Mr McEwen, Professor Galvin distinguished cracks caused by mining using the long wall method as opposed to the cracks identified by and relied upon by Dr Thomas which he says resulted from the subsidence. In long wall mining the excavation is extremely wide and is carried out with a deliberate intention of causing the mine to collapse resulting in maximum subsidence and in turn creating maximum strains and tilts. Cracks in those circumstances can be up to a metre wide. Professor Galvin knows of no example of the mechanism referred to by Dr Thomas in either the textbooks or other literature on the topic of mine subsidence. When asked to assume that the theory put forward by Dr Thomas is correct, Professor Galvin recognised that ultimately the root cause of the subsidence would be the presence of the mine.

58 Early on in the investigation on behalf of the Mine Subsidence Board, Professor Galvin identified the prospect of defective foundations of the structure, the consequence of soil reactivity, the impact of shallow groundwater flows, soil creep and landslip as possible causes of the damage.

59 Subsequently, as experts with more specific qualifications joined in, he ultimately confined his emphasis to an elimination of mine subsidence as the cause of the disturbance and in particular a rebuttal of the theory put forward by Dr Thomas.

60 Professor Galvin maintains uncertainty about the reliability of the so called horizontal vectors demonstrated by the survey results. The vertical components are accepted. Professor Galvin is of the opinion that the way in which the surveyors have indicated the horizontal movement could be wrong. He says there is no evidence to suggest that the structural damage can be attributed to mine subsidence, although a number of further investigations need to be done before he could be absolutely certain. He regards the theories expressed by Dr Thomas as remote. Nevertheless, the reports by Dr Thomas have cause him to give thought to mechanisms that he had not previously considered and should be dealt with as a matter of diligence. He explained that based on his knowledge and extensive experience as well as his own library, the mechanism attributed to the movement which caused the damage, according to Dr Thomas, falls outside that knowledge and experience. He was not prepared to say that the possibility did not exist. He deliberately said that it is remote but he has not eliminated it.

61 Professor Galvin recognises that the soil on the surface at the rear of the house has settled, but relative to when the zero level was established in 1998 that land has risen and fallen. Currently it has settled below the zero that was established in 1998. The graphs developed from the survey records show waves of ground movement coming through. Some of the measurements of the wave motions were only a month apart. At other times there is a gap of up to seven years without any record of what has happened in the intervening period.

62 His answer to a direct question comparing the first survey in 1998 to the last survey carried out in March 2007 he said the following:-

In absolute terms comparing 1998 to March 07 the points are down, they’re lower than 1998. In terms of trends the trends are up, down, up, down, and who knows how many more because of the frequency of the surveys.

63 Professor Galvin agreed that at least two points at the rear of the house namely points identified as 23 and 24 show a trend of downward movement between March 2004 and March 2007.

64 Professor Galvin agreed with Mr Nock that the presence of calcium carbonate on the walls of the mine workings and ironstones stains observed on the video suggest that water has been entering the mine. He also agrees that there is evidence of water flowing through the floor. Professor Galvin explained the presence of the water as follows:

Well those workings are down dip on a very large extensive area that’s already been mined, and it’s common practice particularly in the Lithgow region, that when you get periods of heavy rain, those old workings are all interconnected, and the water makes its way down to the lowest point. And looking at the floor and doing some calculations on the amount of water that must’ve flowed across that floor, leads me to two opinions. One it’s not seepage, couldn’t possibly be made all from seepage from the roof. And most likely given that it’s connected to the old workings, a bit further up in the hill, it’s almost certainly one of the ways of - one of the flow paths for the water when the old workings further up get flooded.

65 He could not agree that the majority of the water found in workings in the Lithgow area came from the surface. However he agreed that the percolation described by Dr Thomas from the surface was a possibility.

66 When challenged in respect of his indication of the prospect that groundwater from a leaking reservoir above Mrs Vervoorn’s house had contributed to the damage Professor Galvin acknowledged in cross-examination that he did not know the course the water took and that he was simply indicating that there are signs of groundwater in the area and it is reporting to the surface at some points thereby providing evidence that there is groundwater flow. He could not say whether the water would have made its way to the back of the house. Although in a report in March 2007, Professor Galvin described observations of considerable ongoing water discharge and signs of ground settlement along a line in the road above Mrs Vervoorn’s house as elementary and essential to determining and validating if subsidence of mine workings is occurring, he agreed in cross-examination that neither of those factors fitted into that category.

67 He also considered that cracks observed underneath Mrs Vervoorn’s house were not approximately coincident with extensive cracking within the house and in the tile pathway to the east of the house. He has not turned his mind to the movement of the house, as his interest has been the movement of the ground. The survey measurements are not taken on the ground but at points on the structure near the ground.

68 He regards the movement of the walls as a separate issue. He noted however, that the eastern and western walls of the house are tilting outwards. He made no observation about the southern wall of the house. He relied on the expertise of others for an explanation of that occurrence. Nevertheless, in a final report prepared in June 2007, he identified the following potential causes for the damage to Mrs Vervoorn’s house as follows:-

i. poor footing design and construction practices (by today’s standards).

ii. reactive soil.

iii. soil creep.

iv. changes in groundwater regime.

69 He then goes on to make positive remarks about the prospect of each one of the factors being a cause and concludes that a combination of the factors has resulted in the damage to the structure. He sums up his opinions in a conclusion as follows:-

i. The possibility/probability that mine subsidence is cause of damage to Mrs Vervoorn’s’ house is extremely remote. There is no factual evidence that points to this being the cause of the associated ground movements. The mine subsidence mechanism proposed by Dr Thomas falls outside my subsidence engineering knowledge base and experience.

ii. There is a range of factual evidence that indicates that ground movement is associated with one or more other factors.

iii. A number of these other mechanisms are likely to be active simultaneously, in particular, reactive soil responses, soil creep and changing groundwater regimes.

iv. The damage to Mrs Vervoorn’s house has materialised because the design and construction of the footings is inadequate to deal with these mechanisms.

70 It is apparent from the cross-examination by Mr Nock that Professor Galvin independently caused the surveyors to reproduce plans and diagrams of plots that related only to movement at or near the ground level of the building. Some were confined to demonstrating the horizontal shift of the house. When challenged by Mr Nock that he was instructing the surveyors to produce evidence supportive of his case, he protested that he was only interested in the information that he requested the surveyors to specify. He summarised his position as follows:-

The surveyors are registered surveyors. They took out the survey. Their work is surveying. They undertook the surveying. How - what they do with the results and how they plot is up to anyone at all to decide what they wanted. Mr Appleyard wants tops, well he can have tops. If someone else wants bottoms, they can have bottoms it’s as simple as that. I did not instruct the surveyors in how to undertake surveying.

71 He nevertheless recognised that the instructions given to the surveyors by him were without direction from the Board. He said “I took them off on my own bat”.

72 It is Professor Galvin’s position therefore that the readings taken at the top part of the wall of the house are not relevant to his interest in understanding how the ground is moving. He did not interpret the wall movements in response to the ground because, as he explained, in subsidence engineering there are two distinct elements namely the effect of mining on the surface and then the effect of the surface on the structure. The effect of the surface on the structure is a domain of the structural engineers and it is not within his expertise. Nevertheless, in March 2007 he made observations about how the damage to Mrs Vervoorn’s house is concentrated and worse in those walls that are orientated down the slope of the hill rather than across of the slope of the hill, including observation about fracture patterns and tilting.

73 Initially he was engaged by the MSB to perform the role of “independent reviewer” in order to ensure that any outcomes were soundly based. Professor Galvin accepts that role was in his capacity as a contractor or servant of the Board where he was being asked to prepare an answer to the claim by Mrs Vervoorn. Subsequently, he said “my role to the Board was to advise them on the merits of the claim”. He started off in the role of providing independent advice to the Board and then as the matter progressed his role changed.

74 At one stage Professor Galvin consulted with a Professor Sullivan in relation to soil stability and soil creep but did not obtain a report. Preparations were made for instructions to be given to Professor Sullivan but it was decided not to proceed after he expressed an opinion that he did not consider landslip was occurring. Professor Sullivan made the following observations in an e-mail to Professor Galvin on 5 March 2007.

3. The vectors need to be rotated 30 deg. Counter clockwise on the attached figure. But nevertheless if you believe these vectors they do show the house is mainly moving south and the retaining walls are moving north! If these are correct it is something not related to down slope creep.

4. …..

I am wondering if we are dealing with a complex series of factors that have changed or are changing over the life of the structure and now contributing differently to what has been observed over the last few years. These factors could include; poor foundations in extension, movements at the front of the house due to retaining walls and other factors??, poor control of roof runoff affecting house foundations causing some settlement in the old part of the dwelling, poor foundations in the old part of the dwelling, soil creep downhill? And lastly mine subsidence/creep?.

75 Professor Galvin denies that he did not pursue a report from Professor Sullivan because he had expressed the views set out above, particularly as they related to subsidence and the movement to the south.

76 Professor Galvin is unable to agree that the survey data shows a trend for the house to be moving in a southerly direction. When asked what he based that opinion on, his answer was as follows:-

Because it’s not showing a trend moving south, it shows that it moves south sometimes and then other periods it moves north.

77 In answer to a further question he answered as follows:-

A trend to me is a long-term thing. I look at a trend and where is it trending, it is not trending south, it is moving south for a while then it’s coming back to north again and then it’s moving north-east. It’s not trending south.

78 After much confusion Professor Galvin agreed that drawings depicting movement between March 2004 and July 2005 showed a horizontal movement of the property to the south. On the other hand, a survey depicting movement between July 2005 and March 2007 showed a movement trending towards the north or northeast. He would not agree that the vertical movement at the rear of the house over the same periods shows the house trending downwards. Rather at the points surveyed the movement is up and down which he says supports his contention that it is probably a combination of factors causing the movement one of which is soil reactivity.

79 He nevertheless agreed in cross-examination that some of the plans show the house moving in an uphill direction and that it would be highly improbable if the cause of the movement was soil creep for the house to move uphill. Between March 2004 and March 2007, five points on the western side of the house are shown as moving uphill. Two points on the eastern side of house are in the same position. Between March 2004 and July 2005 the survey measurements show a 45-degree movement relative to the hill at the rear. Professor Galvin would not be drawn by Mr Nock to agreeing that the movement was uphill, but rather that it shows movement across the hill with an upward component.

80 In conclusion during re-examination Professor Galvin confirmed that he has “a hell of a lot of trouble” with the concept put by Dr Thomas in relation to fines being transported along cracks and down cracks. He says he knows from his experience with numerical models that it is highly improbable fines will be transported down one vertical crack and then along a horizontal crack and down another vertical crack. If he had more time he would have done a numerical model in order to explore the issue further.

81 Mr Nock makes the submission that as Professor Galvin was employed on a regular and ongoing basis under contract with the respondent, he was not able to bring the necessary degree of impartiality to the giving of his evidence to enable the Court to accept him as an expert.

82 Although Mr Nock’s description of Professor Galvin as the “ringmaster” for the preparation of the respondent’s case, overstates the position it is clear nonetheless that Professor Galvin played an active role in marshalling the evidence against the applicant’s claim that the damage was caused by mine subsidence. He overtly negotiated with the surveyor for the purpose of organising plans and diagrams in a form that demonstrated the information upon which he primarily relied to discount the applicant’s case. By itself the negotiation with the surveyor does not mitigate against the acceptance of Professor Galvin’s evidence. However, there is a spate of correspondence which demonstrates that Professor Galvin was intent on defending the Board’s position beyond what might be expected of an impartial expert within the concept of the code of conduct developed in the Court’s Expert Witness Practice Direction. At one point Professor Galvin solicited advice from Professor Sullivan. His opinion was not pursued by any instruction to prepare a report. The enquiry from Professor Sullivan went no further after the exchange referred to above at [74].

83 There is no doubt that Professor Galvin has specialised knowledge and experience in the field of engineering associated with mine subsidence. That is a relevant field of expertise bearing upon the issues in this case. However, Professor Galvin initially took it upon himself to express opinions in fields of knowledge which he ultimately agreed were not his specialisation. Those opinions remain on the record and form part of the respondent’s case.

84 Although Professor Galvin emphatically confirmed that he understood he had a primary duty to the Court to give his evidence in an unbiased and objective manner, it is important, when assessing the weight to be given to his evidence, that his apparent expertise and understanding of his obligations expressed in the witness box be balanced against his long and intimate association with the Board as a consultant and the pivotal role he has adopted in managing the development and presentation of the evidence.

85 In order to clarify the survey evidence generally and to resolve disputes about what the readings demonstrate it became necessary to hear evidence from the surveyor Mr Grosfeld. He was called by the respondent.

86 Mr Grosfeld confirmed that from time to time he acted on instructions from Professor Galvin, Mr Appleyard and Mr Hawkins in addition to officers of the MSB. He carried out survey work as requested by the three witnesses. He received requests to prepared different types of survey documents and drawings from the three witnesses. He was not aware of the purpose of preparing the survey documents. The instructions were to place marks on the house and monitor them. The bottom marks near the ground were used to measure the movement of the structure at that point.

87 Mr Grosfeld was able to identify the documents which were altered in accordance with instructions from Professor Galvin together with the bundle of plans ultimately forwarded to the MSB on the 28 May 2007, all of which have been adjusted to take account of the adoption of a stable datum following the discovery that the State marks used for that purposes earlier were not stable. None of the documents redrawn at the request of Professor Galvin were altered in respect the levels and locations. It was merely a change to the way in which they were displayed or represented.

88 In cross-examination Mr Hawkins confirmed that the instructions he received from the Board were to answer the specific question whether the cause of the damage was mine subsidence or not. He carried out shrink/swell tests early in the process to see if any clear alternative causes were visible. He was not asked to carry out a detailed investigation into the actual cause. In the course of carrying out his instructions he had communications with Professor Galvin and with Mr Appleyard. Mr Hawkins did not form a definitive view as to what might have caused the problem with Mrs Vervoorn’s house other than he said he was sure it was not mine subsidence. He confirmed that as a consequence of Professor Galvin raising the question of slope stability, he looked at the question “at least peripherally”. He was not informed when he wrote his original report that the matter was subject to Court proceedings. He understood that the MSB used Professor Galvin as a review consultant for most of the reports provided. Mr Hawkins regarded slope instability and landslip as the same thing and formed the view that it was a “possible or causable contributor”. However he thinks its is probably unlikely but is rated more likely than mine subsidence. When asked on what evidence he based that opinion he gave the following answer:-

We’ve got strange differential movements over the house, some of those points that are moving are moving in that direction of maximum dip of the coal seam and given that something is moving in the direction of the maximum dip, you have the possibility it’s moving down dip. Unfortunately we’ve got no stable datum that is not on top of the coal seam. All we’ve seeing is a differential movement. So if the lots moving downhill together, with some faster than others, you’re going to see the sort of strange differential movement, some point moving up and down.

89 He agreed that it could not “be the possible sole cause”. Mr Hawkins confirmed in cross-examination that he would require “a whole lot more data” before he could confirm that the cause was not mine subsidence.

90 Although he is not an expert on the construction and design of foundations he has sufficient experience as a geotechnical and engineering geologist to know that foundations are inadequate or can be inadequate. He regards the foundations in this case as being a possible or plausible cause for the damage to Mrs Vervoorn’s house. When he signed off on a statement in a joint report that, on the balance of probabilities the damage to the residence has not been caused by mine subsidence and that there are other possible and plausible causes that singularly or in combination have caused the damage, these including poor foundation design, he did so relying on Mr Appleyard’s stated opinion. In cross-examination he explained that until a foundation is investigated one cannot rule out poor foundation design. No one in this case has dug and exposed the footings and properly investigated them. The subject footings were not exposed.

91 Mr Appleyard had told him that he felt that it was sufficiently visible under the house for him, to form his opinion. Mr Hawkins accepted his view as a structural engineer.

92 When asked about the prospect of an effect from groundwater, Mr Hawkins gave the following answer:-

I could see piping up near the reservoir. I thought it was an awful long way away. On the other hand, Mrs - I’m sorry, in the report by GHD-LongMac, they referred to Mrs Vervoorn’s statement that water had discharged and that it was relevant. I also noted that the retaining wall on site immediately behind her house, there’s a dish drain that was clearly younger than the wall so I would conclude it was not impossible that groundwater seepage had come from the reservoir given what I was being told but I saw no evidence of it at the time but it was sometime after the alleged incident.

93 Ultimately, he was unable to say whether the damage was caused by groundwater one way or the other. Nevertheless, he was prepared to go along with Mr Appleyard and Professor Galvin to say in the joint report, without any investigation, that the foundations and groundwater effect were possible and plausible causes in relation to the damage.

94 Mr Hawkins was emphatic that he could eliminate mine subsidence as one of the factors causing the cracking in the structure, in the front of the house. Soil creep is definitely a factor on the steps and probably the front of the house but it is less likely to be a factor at the rear of the house not withstanding the stature of certain trees which have grown with a bend against the hill. In discerning between the factors which have had effect at the front and the rear of the house respectively, Mr Hawkins agrees that probably some factors applied to the front that do not apply to the rear and vice versa, but they are not necessarily a totally different set of factors. His opinion is the damage at the front corner of the house is related to soil creep which manifests in both a horizontal and a vertical movement. Although where there is a variation in slope with a flat area between two steep areas, the movement across the intervening flat area might be limited to a horizontal movement. That circumstance is unlikely to have occurred in this case.

95 According to his observations Mr Hawkins says that there has been horizontal and vertical movement at the front and rear of Mrs Vervoorn’s house but there is comparatively little horizontal movement in the main part of the house in the middle. In his opinion, the horizontal movement at the rear of the house is not related to soil creep, because during the survey periods the direction of movement is shown as being in a horizontal fashion uphill or a side ways movement across the hill.

96 In his view the groundwater flow observed in the bores is not coming from the reservoir above the house. It is natural groundwater in the slope. He does not think that the damage at the rear of the house is related to the groundwater flow he observed in the bores.

97 He could not eliminate the possibility that landslip or reactive soils had played a part in causing the damage at the rear of the house. However, he has no information in regard to the state of the house since 2005. He had not being able to return to the site since 2005, as the MSB would not pay his fees. Moreover the MSB would not facilitate providing him with rainfall patterns for relevant periods to enable him to consider the effect of weather on soil reactivity. Having regard to the slight to moderate nature of the soil reactivity he would expect movements to be in the range of up to 10mm to 30mm under normal climatic conditions without interference from outside sources.

98 Mr Hawkins agreed that in the surveys taken from 2005 through 2007 a downward trend is shown at the rear of the house. He agreed that a downward trend is inconsistent with soil reactivity being the sole cause of the movement.

99 Mr Hawkins left any observations regarding the foundation designs to Mr Appleyard. Mr Hawkins agrees that if he had been presented with the survey results alone there would be nothing in that material that would be inconsistent with showing that there was soil subsidence.

100 Although he could not agree that the rate of the downward trend was faster than he would have expected with soil reactivity being the cause he did agree that the movement shown during the period of the survey is greater than he would normally expect from that cause.

101 Mr Hawkins says, that none of the mechanisms identified by him account for the vertical movement of the building in a downward direction.

102 The following question and answer explains his position:-

Q. If nothing is happening underneath in the mine would you have expected the house to still continue to go down from any of the other sources?

A. Not from the ones that are in my area of expertise.

103 In re-examination Mr Hawkins gave the following explanation to Mr McEwen:-

Q. While you were still dealing with this before my learned friend took you to reactive soil you were asked a question concerning horizontal movement in the context of being left with groundwater flows and you said something to this effect, “In relation to horizontal movement it’s towards the maximum dip, if there’s movement on the bed or the plane any movement together with and differential to the joints then you can get a change”.

A. Yes.

Q. What are you referring to there?

A. Okay. We’ve got a coal seam dipping down towards the road, above that we’ve got a carbonaceous clay stone seam which would have ..(not transcribable)..dipping towards the road. We’ve got groundwater moving through the top strata which is partly a lubricating but also applies an uplift pressure to reduce shear strength. There are well documented large slides on that sort of situation, like at spears point and coal point in Newcastle. It is possible that you’re getting a slow landslip that would be under the Australian guidelines of geomechanics for classification be described as an extremely low - extremely slow slip where the whole lot is moving together. That only causes damage where you get differential movement but the sense of movement that you record on the monitoring points if your monitoring point is on the slide your sense of movement can be - for instance if the garage is the monitoring point, if it moves down slope or down dip further than the rear of the house then you actually get an apparent up slide movement at the rear of the house.

Q. Why is that?
A. Because you’re taking the zero as the garage.

Q. Does any of that motion you’ve described to us just now bear any relationship to the void under the house?
A. No.

Q. Is it impacted at all by the minings at all?

A. I don’t believe - I don’t believe so because if it was I think there’d be collapse at the coal top above the workings.

104 In re-examination Mr Hawkins was still not able to explain the additional movement over and above that he would expect from reactive soil under normal circumstances. He agreed in re-examination that the measured rise in the bottom mark at one point on the rear of the house between 2005 and March 2007 reflected a change in the trend of the downward movement and in relation to that corner of the house it would cause him to review the answers he gave earlier in relation to the downward trend. However, no explanation as to the result of the review was offered.

105 Mr Appleyard explained his understanding of the view taken by Professor Galvin as to the desirability of representing survey data with red or green arrows as follows:-

A. I expressed the view to Professor Galvin that the use of the red arrows which contained both the magnitude of horizontal movement and also the direction were of value. I also expressed the view that the use of the green arrows may be confusing to a lay reader because their primary function was to convey the magnitude of vertical displacement. The way the surveyor had drawn them, and this wasn’t a criticism of the surveyor, he had done it perfectly correctly in terms of procedure, but he’d drawn them all in a north-south direction, and it was and is my view that that could have been, could have been misleading were it not explained to a lay interpreter or a lay reader

106 Mr Appleyard described the nature of his role in advising the MSB in the following context:-

Q. You do however state that on the balance of probabilities the damage to the residence has not been caused of mine subsidence, so I assume I’m dealing with you in your field at the moment that you did not completely rule out mine subsidence at any time?
A. I think in at least one of my reports, and I can’t identify which one, but I know that in at least one of them I have used words to the effect that given the acknowledgement that there are old workings beneath Mrs Vervoorn’s residence it would be quite incorrect to rule out the possibility of mine subsidence as playing a role.

Q. But you then agree with your other experts about the other possible causes, that right?
A. Yes that's correct.

Q. Do I take it that your instructions from the board were to deal only with the question of whether or not it was mine subsidence and not deal with other possible causes?

A. No. My instructions weren’t put in those terms. My instructions were to provide advice to the board through Mr Greg Cole-Clark as to what in my view was the likelihood of the damage being due to mine subsidence and/or being due to other factors.

107 Mr Appleyard considered himself able to give an expert opinion as to the likely effect of reactive soil within his expertise. However he did not regard himself as being sufficiently knowledgeable technically to give a report or expert evidence in respect of soil creep, landslip and groundwater flow except in concert with others. He deferred to the opinion of Mr Hawkins in relation to soil creep.

108 Between 2005 and 2007 Mr Appleyard noted a greater intensity of cracking in some areas of the house. He regards the subfloor construction of the house as being quite substandard and as a result the southwestern corner of the residence has subsided. He took photographs of the footings and foundations, which in his opinion are evidence of “very, very poor and questionable construction”. He agreed however, without further investigation, that he was not able to demonstrate any sign of subsidence of the brick piers. It would be necessary to establish a bench mark a plane or laser level before any conclusion could be drawn. He agrees that the rear of the house has subsided in the southwestern corner. That his position is equivocal is explained by the following question and answer:-

Q. Well is there anything there that indicates to you that the foundations or the brick piers and the like have caused that subsidence?

A. I believe the footings in the specific area of the southwestern corner are bearing a significantly higher load per unit of length than the footings around the remainder of the residence and it is my belief that they have settled. I believe they have settled for a number of reasons, not just straight out settlement into the ground. Now I have a problem here. It is very, very difficult to get into that corner. I don’t know and I don’t think any of the other experts can put their hand on the heart and say they know exactly how those footings are constructed. I have my opinions but we just don’t know and unless we had done some invasive testing which means really digging up either externally or internally and externally would be the only logical way to do it, we just don’t know. But I can draw certain conclusions from what I saw under the house.

109 Mr Appleyard was asked what he would expect to see if the foundations were subsiding and gave and answer as follows:-

Q. Mr Appleyard if the foundations were subsiding and they were subsiding because of the weight of the house on them or being improperly built, what would you expect to see in relation to, first of all, the outside of the house, what would you expect to see?

A. I would expect to see some cracking in the walls at the junction between the southwestern walls - I should say the southern walls and the western walls with the remainder of the house and there is. I would expect to see the sort of settlement that you can see beneath the timber roof plate and I would expect to see an outward movement at the top of the wall

110 Mr Appleyard agrees with Mr Nock that there has been no observable evidence in the form of damage restricted to the foundations and the sub-foundation material under the house. He did not report to the MSB in those terms.

111 Although in a report dated 27 July 2004 Mr Appleyard made the observation that the subfloor construction of the house is quite substandard and as result the south western corner of the residence has subsided it became apparent in cross examination that he had not been able to inspect that area under the house as it was “virtually impossible to get into that area”. Moreover, he explained that if one examines coursed brick footings for damage it is very difficult to pick up cracking in the joints. Even if there is such cracking the effect is made manifest in the superstructure in a much greater way because of the magnification effect.

112 Mr Appleyard does not suggest that the rear of the house is suffering from down slope creep in isolation, but the damage may have something to do with slope instability. He does not think there is a single cause of damage. It is a combination of causes. The survey data has consistently told him that there is a combination of mechanisms taking place which have contributed to the damage to the residence.

113 In a position statement prepared for the purposes of an expert witnesses conference on 13 March 2007, Mr Appleyard concluded that the damage to Mrs Vervoorn’s dwelling was the result of three failure mechanisms described as follows:-

6. I have informed the opinion that there are three (3) failure mechanisms acting in concert with each other.

6.1 The single most predominant mechanism is clay swelling beneath the dwelling leading to a “heave” effect. This is clearly evident from a resolved vector analysis based on survey data provided by Craven Elliston & Hayes.

6.2 The second mechanism is down slope creep which has affected principally the front (northern) verandah and access steps, and which is also clearly evident in the retaining walls between the northern wall of the dwelling and Birdwood Street.

6.3 The third mechanism is that of the “settlement” of the addition at the southwestern corner of the dwelling.

The lack of documentation requires a degree of speculation but my view is that the settlement (and associated wall rotation) is the consequence of inappropriate and unsound construction.

6.3.1 The area occupied by the (5.0m X 1.5m) addition was originally a verandah most probably timber.

6.2.3 The most likely method of support for the verandah would have been a brick skirt wall on coursed brick footings, probably no more than 200 – 300 mm in height.

6.3.3 I suspect that the timber flooring was removed and replaced by corrugated steel “sacrificial formwork”. A concrete slab was then poured on top of the sacrificial formwork to a level which would match the internal floor level.

6.3.4 The perimeter of the slab is poorly supported and it has “settled” across the 5.0 m length of the southern wall of the dwelling.

114 Finally he said in that statement that he did not believe that there is any evidence “yet available” which would support a positive proposition that the damage is linked in any way with mine subsidence.

115 When cross examined about the statements on 13 March 2007, Mr Appleyard gave the following evidence:-

Q. Now you say that you never ruled out mine subsidence, is that what you say?

A. Not quite. In paragraph 7, and I chose this word deliberately, I do not believe that there is any evidence yet available which would support a positive proposition that the damage is linked in any way with mine subsidence. Now the word ‘positive’, I was using it in the context that in Dr Ambrose’s analysis or Dr Thomas’s analysis, nothing positive had been shown to me that supported the proposition that mine subsidence was the cause. It was always by default. It was never a positive conclusion. That was why I used the word ‘positive.’ But when I referred a moment ago to having never discounted mine subsidence - and again I don't have the document in front of me - I have on a couple of occasions said the house is build over old workings. It would be very, very silly to discount the possibility that mine subsidence could be a factor.

116 The following exchange then took place:-

Q. Let’s deal with the foundations of the house. Do you say now that there is positive evidence that shows that the foundations of the house were causing any of the damage to the rear of Mrs Vervoorn’s house?

A. No.

117 He was also unable to point to any evidence that is positively related to the mechanism of clay swelling beneath the rear of the house leading to a heave effect. Likewise, he was not able to say there is positive evidence which shows the rear of the house is affected by soil creep. His identification of the three likely mechanisms is based on his interpretation of the survey data. Mr Nock then asked the following question and Mr Appleyard answered as shown:-

Q. Well then you say there is evidence?

A. There’s undoubtedly evidence of movement of the superstructure of that house. You have put to me on a number of occasions can I point to an instance in the brick footings of the house and say there is damage, there is a causal link between that bit of damage and that bit of damage in the superstructure and I’m saying I can’t do that.

118 The following exchange in respect of the March 2007 document followed shortly thereafter:-

Q. The question was this, your three theories that you’ve put in this document that’s in front of you, where you’ve agreed their (sic) theories, and what I’m suggesting to you is this, that nowhere did you find any evidence whatsoever that those three theories were acting either individually or in concert did you?

A. I can’t answer that in a yes, no, sense, I’m sorry Mr Nock. I believe the answer I gave before your Honour in relation to the survey data is the correct answer.

119 On 19 April 2007 Mr Appleyard suggested to Professor Galvin that there should be a strategy meeting with counsel in relation to the evidence. Following discussions with Professor Galvin about whether alternative surveyors should be engaged he made the following observations in an e-mail:-

Contrary to what I said on Wednesday, I believe we should stay the course with CEH. I say this because of several factors.

First, they have a wealth of data over a long period which cannot be replicated. If necessary, we could even ask for access to field books etc. We may not be comfortable with many of their reports, ambiguities, definitions of reference points, adjustments etc but all of these issues can be addressed in the course of face to face discussions with them. In other words, we are not questioning their data bank, we are questioning what they have done thus far with that data.

Second, it may weaken our position to suggest bringing in another firm to carry out some form of “forensic analysis” of the CEH data. I believe we are in a position to do the forensic work ourselves in direct discussions with CEH.

Finally, it may in fact enhance our position if we are able to work through the data with CEH, rectify the anomalies and then arrive at an acceptable outcome. Obviously I can’t yet predict where this might end up but the latest document from CEH gives me considerable optimism. The down slope pattern is even more consistent than my crude vector diagram suggested on Wednesday.

120 He agreed that at the time there was consideration as to whether or not the current firm of surveyors should remain in the case. When asked whether he considered that the advice passing between himself and Professor Galvin was relevant to his area of expertise, he explained as follows:-

Because in April this year I think it is now common ground that we and indeed Mrs Vervoorn’s experts thought there were some errors in the - not only thought we knew there were some errors in the survey analysis. This email stems from discussions Professor Galvin and I had as to whether we should perhaps ask somebody other than Craven Elliston Hayes to look at the data and give advice or whether we should in fact meet with Craven Elliston Hayes. We had given thought to asking another firm to look at it, but as I say here having given it some thought I went back to Professor Galvin and said no I don’t think that’s the right course of action. I think we should sit down with Craven Elliston Hayes in conjunction with Mrs Vervoorn’s experts and meet with them and that’s exactly what we did.

121 When asked in re-examination whether he was able to say there is some connection between the observable damage and subsidence of the structure and the footings and subfloor, Mr Appleyard gave the following explanation:-

We know very little about the actual construction of the south-western extension. There’s a very rudimentary drawing, the one that’s just gone into evidence. All we know is that there is a suspended concrete slab supported on a multiplicity of elements which are transferring the load from that slab to a perimeter footing of some sort, construction undefined. But it is possible to say mathematically that the load that that perimeter footing must be bearing because of the weight of the slab is different from the load on the coursed brick footings throughout the rest of the house.

122 Further on he says:-

Viewed from beneath the house, beneath the floor, and looking into that southwestern corner, I can see that the perimeter of the slab appears to be supported by some loosely stacked brickwork, that’s the best way I can describe it.

123 He went even further later on when asked whether he could draw certain conclusions from what he saw as follows:-

Yes I can. This form of construction is incredibly unorthodox, to put it at its best. Normally one would not support a concrete slab of any sort on timber bearers, and here we clearly see a concrete slab supported on timber bearers. I don’t know the structural capacity of that yellow beam, but it’s clearly slender by comparison with the sort of beam that we would use in, if I can just put it this way, more orthodox construction. And what I don’t know, and I’m being as honest as I possibly can here, I don’t know what’s happening around the perimeter of that slab other than that those bearers, the timber bearers and the yellow mine stringers, must clearly be supported on some form of perimeter footing. Most probably brickwork again. I’m also strongly suspicious that that material there that the perimeter is founded in is liable to settle, because it would have to have been placed material, after the original verandah was demolished and the building was extended.

124 A further answer was along the same line when he was asked whether he wished to review the opinions expressed as follows:-

…..my view is that we have a cocktail mix of mechanisms. To summarise them, I believe the southwestern corner of the house, the extension as we referred to it, is or has settled as a consequence of poor construction and possibly inadequate compaction of the fill material that it’s founded on. I’ve said several times it’s very difficult to be too precise because of the limitations of access and so on. I believe the damage in the main to the external and internal brick walls of the residence is due primarily to reactive soil effects, and they can be both hogging and sagging. In other words they can be positive and negative depending on climatic conditions. And I believe thirdly that there is a component of damage due to either landslip or soil creep or down site movement. And that is clearly evident in the case of the front verandah. You can see it, you can see the rotation of the front steps and the front verandah. You can see the rotation of the walls of the side boiler house away from the residence. And I put that down to perhaps a combination of reactive soils and inadequate footing construction.

125 Finally in answer to a question from the bench, Mr Appleyard made the following comment:-

Q. If Dr Thomas’s theory is right and you got the sort of movement below the house that could be attributed to the causes he hypothesised, which of soil creep, or landslip or reactive soils would give a similar reaction to that which you’d get from that type of activity?

A. It could be either reactive soil movement or landslip movement.

126 Lastly in re-examination he again explained how he came to form the view that it would be beneficial to consider whether other surveyors ought to be retained in the following answer:-

My view was that the reliability of the survey date (sic) that we had been given by Craven Elliston Hayes was in some doubt, and that as a consequence of that perhaps, if I can use the term, we, meaning experts acting jointly on behalf of the board, may consider seeking further external - advice from another firm of surveyors. On reflection I felt, I felt and I expressed it in an email that Mr Nock showed me this morning, that really we would be better working with Craven Ellison & Hayes identifying any errors or anomalies, and having the data recast, and ultimately that is exactly what happened.

The alternatives to mine subsidence

(1) Reactive Soil

127 Mr Kotze a witness with the relative specific expertise carried out soil tests. He concluded shrinks/swell related to reactive soils has not (having regard to its extent), caused the damage. Dr de Ambrosis also formed the view that the ground settlement was too large to be due to soil reactivity.

128 By a process of elimination Professor Galvin reached the conclusion that the most likely causes of damage is reactive soil in conjunction with a number of other parameters namely poor footing design, soil creep and changes in the groundwater regime. His conclusions in relation to soil reactivity are not positive. They are derived in the context of eliminating mine subsidence.

129 Although expressing a view that soil reactivity had played a part Mr Hawkins was not able to explain the observed additional movement beyond the normal expectation of the consequence of soil reactivity.

130 Mr Appleyard professed expertise in relation to soil reactivity. He expressed a belief that the damage to external and internal brick walls is due primarily to reactive soil effects, namely hogging and sagging. However his concentrated concern in relation to the rear section of the house was in respect of foundations.

(2) Landslip

131 Mr Kotze found no evidence of large scale or even significant landslides or landslip. Professor Galvin only identified it as a possibility at the early stage of the investigation and did not pursue it. Nevertheless, Mr Hawkins identified slope instability or landslip as a possible or plausible contributor. However he says that if it is present it would be rated as extremely slow.

132 Mr Appleyard maintained a belief that there is a component of damage due to down site movement that could include landslip.

(3) Groundwater

133 Professor Galvin initially placed some emphasis on the history of water travelling down hill from the reservoir in the direction of the house but was not able to maintain his pursuit of that prospect with the same vigour, as the case progressed.

134 Mr Hawkins was unable to say one way or the other, although initially he agreed to concur with the opinion of Professor Galvin, without any investigation.

(4) Soil Creep

135 Having regard to the age of the house, Mr Kotze expressed the view that it would not be soil creep that was adversely affecting the house, particularly the core of the house. There is no evidence that he could find, that demonstrated slope creep had occurred around the rear and central portions. Dr de Ambrosis agreed that the crack pattern in the house is not consistent with soil creep. Moreover, hinging is not caused by soil creep.

136 Professor Galvin conjectured that soil creep contributed to the cause of the damage together with the other mechanisms acting simultaneously. Mr Hawkins also recognised the prospect of soil creep being a contributing factor. Professor Sullivan expressed a preliminary view that a changing complex series of factors could be contemplated, although the movement demonstrated by the plotted vectors in a southerly direction eliminated down slope creep. Nevertheless, he maintained the prospect of soil creep down hill as a factor relating to the damage at the front of the house.

137 Professor Galvin agreed that if in fact the house was moving uphill then soil creep would be an improbable cause of the movement. Mr Hawkins’ opinion is that damage at the front of the house is due to soil creep but that the horizontal movement at the rear of the house is not due to soil creep.

138 Mr Appleyard deferred to the opinion of others on this aspect. He nevertheless ventured a view that the damage at the rear may be related to slope instability but he was not able to say there is positive evidence which shows the rear of the house is affected by soil creep. However, he believes there is a component of damage due to soil creep that is clearly evident in the case of the front verandah.

(5) Inadequate Foundations and Footings

139 Dr de Ambrosis could find no indication of footing settlement.

140 Mr Appleyard is the witness primarily relied upon by the respondent in respect of this issue. Despite the shallow nature of the footings Mr Appleyard could not find any damage as a consequence of ground strain transfer. His main argument rests with the alleged unorthodox construction of the underfloor system in parts of the house. He was unable to investigate the footing system at the rear. He speculates that the foundation material under this part of the house is wetter than elsewhere. He says that inadequate footings at the front of the house have allowed the front stairs to break away. There is a like occurrence along the western side of the house.

141 However, he agrees that without further investigation he could not show conclusively that the brick piers had subsided. Moreover he could not point to any observable damage to the foundations. Nor could he establish a link between the construction of the foundations and the damage to the house.

142 The issue of inadequate constructions of footings is amongst the number of factors that Professor Galvin includes as a possible contributing cause to the damage. Professor Sullivan muses to the same effect in an e-mail to Professor Galvin on 5 March 2007.

143 Mr Hawkins describes the foundations as being a possible or plausible cause for the damage to Mrs Vervoorn’s house. He was nevertheless ultimately relying on Mr Appleyard’s stated opinion to list it as one of the possible and plausible causes.

144 Without having to resort to accepting the submission by Mr Nock that the collusive approach to collection and presentation of the evidence by the experts retained by the respondent means, that their evidence should be rejected, I have not been persuaded on the balance of probabilities that the damage to the core and rear sections of the house is solely as a direct consequence of the presence of reactive soils, landslip, groundwater movement, soil creep or inadequate foundations and footings. They may have collectively rendered the house more vulnerable to damage but, even in combination, I am not satisfied it is more likely than not that the damage would have occurred without there being a further major catalytic, innovative, primary or initiating cause.

The effect of Mine Subsidence

145 The survey data shows that the rear or most southerly section of the house has both risen and fallen over the period of survey although the overall trend is in a downward direction vertically and into the hill horizontally. According to the evidence, on balance, that movement is consistent only with the presence of reactive soils or subsidence. There is no categorical opinion expressed by any expert consulted by the respondent that demonstrates a confidence that the cause of the damage in the centre and rear of the house is the direct consequence of any of the other factors postulated by Professor Galvin. Given that the respondent’s case has been developed on the basis that mine subsidence is eliminated as the cause of the damage in those sections of the house its witnesses have not established on the balance of probabilities that any other cause is solely or principally responsible.

146 Mr Appleyard, could not rule out mine subsidence. Nor could Mr Hawkins reach a definitive alternative answer because he was limited by his brief and the extent of the enquiries he was permitted to undertake. When pressed about the prospect of mine subsidence Professor Galvin agreed that the percolation theory of Dr Thomas was a possibility.

147 The survey data is almost entirely derived from measurements taken at points on the structure itself. Whereas Professor Galvin believes that the only reliable indication of whether mine subsidence has taken place is for measurements of the actual ground movements at the surface.

148 Mr Appleyard conceded that if Dr Thomas’ theory is accepted then the type of movement could also be attributed to reactive soil or landslip. However neither of those actions are supported by the evidence as being other than a possible contributing factor.

149 Not one witness has debunked the theory put forward by Dr Thomas in a plausible or acceptable way to the point where it should be excluded. The lack of any previous instance known to Professor Galvin does not demand that the evidence of Dr Thomas should be disregarded. No witness has been prepared to totally and completely eliminate the possibility that the movement under Mrs Vervoorn’s house is associated with the abandoned workings. They are situated immediately below it. Rather than starting with the prospect or likelihood that some other cause has intervened to bring about the damage, logic dictates that the immediate presence of the T-intersection would raise the possibility.

150 Mr Kotze notes the extent of cracking in the house is entirely inconsistent with soil reactivity and Mr Hawkins was not able to explain the additional movement over and above that he would expect from any change in reactive soil.

151 The evidence of Dr de Ambrosis is significant. It assists me to reach a conclusion based on the balance of probabilities. Firstly, the ground settlement at the rear exceeded the consequence of any soil reactivity. He discounted soil creep because of the crack pattern in the house. He also disregarded footing settlement in the absence of any indication that it had occurred. His explanation of the hinging movement described at [37] above, and the rationalisation of the irregular movement measured by the surveyor is a corroboration of the concern that caused Mr Kotze to seek advice from him. The concern arose as a consequence of an observation that the cracks in the house were most often more widely open at the top.

152 Mr Kotze and Dr de Ambrosis state that initial lowering of the back of the house would have been required to produce the hogging cracks in the side walls. The cyclic periods of rising and falling, which concerned the MSB’s experts is adequately explained by the hinging action. However there is no doubt in my mind that the damage to the front section of the house, comprising the verandah and steps in particular, is in no way related to the sinking or settlement that has occurred in the area affected by the mine workings, namely the centre and rear of the house.

153 It is not an easy task to apportion the damage that is attributable to the presence of the mine workings. Although this is not a classic case of collapse where for example the mine roof has caved in, nevertheless, the presence of the abandoned mine has contributed in a major way to the damage caused by sinking or settlement of the rear section of the house which carried through into the main part. The CCTV shows that the roof and pillars are substantially intact in the sense that they have not collapsed but I am satisfied that the truncation of the stratum that created a void has facilitated the process described by Dr Thomas thereby enabling the surface to subside or settle to a degree that is sufficient to destroy the stability of the house structure in the southern section and to an extent that would not have occurred solely as a consequence of any other identified potential factor. The CCTV demonstrates significant intrusion of water trickling into the mine including from the roof.

154 There was a great deal of confusion, disagreement and debate about the accuracy and implications to be drawn from the survey information. This was generated to a large extent by the alarm created by Professor Galvin in his attempts to distance the presence of the old workings from the damage to the house. Ultimately, nothing turned on the problem encountered by the surveyor as a consequence of unstable State marks as he was able to establish a workable and accurate relationship with other stable marks in the sandstone floor of the garage. The perceived problems of the orientation of the north point in respect of the property proved to be a distraction without merit. All measurements were relative and capable of providing to provide a proper demonstration of the movements that have occurred.

155 The applicant recognises that the damage to the front of the house cannot be attributed to mine subsidence. The steps and the verandah of the house are subject to soil creep. The soil creep is not related to mine subsidence.

156 I have preferred the evidence of the applicant’s witnesses who I perceived to be balanced and unbiased. In my view they have striven to present their evidence in a neutral and straightforward way. Although the experts engaged by MSB were retained with an overriding instruction to disprove any impact from mine subsidence and took steps to present what they believed was a best case scenario from the point of view of the MSB. I have not found it necessary to take the position contended for by Mr Nock and reject their evidence entirely in order to reach a conclusion.

157 The house has been destroyed for habitable purposes. The major contributing cause of that damage is the settlement at the rear end due in major part to the presence of the abandoned mine workings. I estimate, doing the best that I can, taking account of the unrelated damage at the front, that the proportion of the damage assigned to mine subsidence is more than half. I determine it to be 60 percent.

158 The parties have agreed that an assessment of a percentage of damage will be sufficient to enable a commercial settlement to be reached. I therefore find that the owner, Mrs Vervoorn is entitled to compensation for damage to her house pursuant to s 12 of the Mine Subsidence Compensation Act 1961 in such sum as represents 60 percent of the value of the house and other improvements on the land other than any improvements situated forward of the house in the direction of Birdwood Street.

159 The exhibits may be returned.

CITATION:	Vervoorn Maria v Mine Subsidence Board [2007] NSWLEC 538
PARTIES:	APPLICANT Maria Vervoorn RESPONDENT Mine Subsidence Board
FILE NUMBER(S):	30558 of 2006
CORAM:	Talbot J
KEY ISSUES:	Mine subsidence :- Proof of cause of damage - extent of attributable damage - appoinment.
LEGISLATION CITED:	Mine Subsidence Compensation Act 1961 s 12, s 12A, s12B
DATES OF HEARING:	25/06/07, 26/06/07, 28/06/07, 29/06/07, 19/07/07, 20/07/07, 25/07/07, 30/07/07, 2/08/07, 6/08/07
DATE OF JUDGMENT:	29 August 2007
LEGAL REPRESENTATIVES:	APPLICANT Mr D G T Nock SC SOLICITORS Barry F Cosier & Associates RESPONDENT Mr P McEwen SC SOLICITORS Trisley Kilmurray Lawyers